Chromium in Drinking Water

🩨 Health Effects

The EPA MCL covers total chromium. Trivalent chromium (Cr-III) is an essential nutrient at low levels. Hexavalent chromium (Cr-VI) is a probable human carcinogen and can cause allergic dermatitis and respiratory problems. Made famous by the Erin Brockovich case in Hinkley, CA.

📍 Sources in Water

Chromium occurs naturally in rock and soil. Cr-VI is also discharged from electroplating operations, leather tanning, and industrial cooling towers. Natural deposits are found across the West; industrial contamination is site-specific.

✅ What To Do

Standard carbon filters do not effectively remove hexavalent chromium. Use a reverse osmosis or ion exchange filter rated for chromium removal. Community water systems are required to test and treat for total chromium.

📜 Regulation History

The EPA set the total chromium MCL at 0.1 mg/L (100 ppb) in 1991 under the Phase II rule. There is no separate federal MCL for hexavalent chromium (Cr-VI), though California adopted a state MCL of 0.01 mg/L (10 ppb) for Cr-VI in 2014 (later withdrawn and being re-evaluated). The WHO guideline for total chromium is 0.05 mg/L, stricter than the US standard.

🔬 How To Test Your Water

Standard water tests for total chromium cost $20-$40 at certified labs. Testing specifically for hexavalent chromium (Cr-VI) is more expensive ($40-$75) and requires a separate analysis method. Home test kits for chromium are not widely available; lab testing is recommended.

💧 Which Filters Remove Chromium?

Reverse osmosis (NSF/ANSI 58 certified) is the most effective home treatment for both Cr-III and Cr-VI, removing up to 95%. Strong-base anion exchange resins can also remove Cr-VI. Standard activated carbon filters are not effective against hexavalent chromium; look for NSF/ANSI 53 certification specifically for chromium reduction.

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